John Renn or Wren

Hi, I am trying to find information about my great grandfather John Wren or Renn. He was shot to death in New York City around 1917-1927 ?After his death, his wife may have dropped the W and made our last name Renn in fear for her safety. (He was an Irish gangster)His only child was Howard Renn Sr. (my deceased grandfather) I believe his wife's maiden name was Moran and he had brothers in NYC.If anyone has any further info, please contact me at Napster383@aol.com Thank you,Howard Renn III